SPACE
The hottest catalog of the year: the most comprehensive list of slow-building solar flares yet
IMAGE:
THIS IMAGE, TAKEN ON AUG. 5, 2023, SHOWS A BLEND OF EXTREME ULTRAVIOLET LIGHT THAT HIGHLIGHTS THE INTENSELY HOT MATERIAL IN FLARES AND WHICH IS COLORIZED IN RED AND ORANGE.
view moreCREDIT: (CR: NASA/GSFC/SDO)
Solar flares occur when magnetic energy builds up in the Sun’s atmosphere and is released as electromagnetic radiation. Lasting anywhere from a few minutes to a few hours, flares usually reach temperatures around 10 million degrees Kelvin. Because of their intense electromagnetic energy, solar flares can cause disruptions in radio communications, Earth-orbiting satellites and even result in blackouts.
Although flares have been classified based on the amount of energy they emit at their peak, there has not been significant study into differentiating flares based on the speed of energy build-up since slow-building flares were first discovered in the 1980s. In a new paper in Solar Physics, a team, led by UC San Diego astrophysics graduate student Aravind Bharathi Valluvan, has shown that there is a significant amount of slower-type flares worthy of further investigation.
The width-to-decay ratio of a flare is the time it takes to reach maximum intensity to the time it takes to dissipate its energy. Most commonly, flares spend more time dissipating than rising. In a 5-minute flare, it may take 1 minute to rise and 4 minutes to dissipate for a ratio of 1:4. In slow-building flares, that ratio may be 1:1, with 2.5 minutes to rise and 2.5 minutes to dissipate.
Valluvan was a student at the Indian Institute of Technology Bombay (IITB) when this work was conducted. Exploiting the increased capabilities of the Chandrayaan-2 solar orbiter, IITB researchers used the first three years of observed data to catalog nearly 1400 slow-rising flares — a dramatic increase over the roughly 100 that had been previously observed over the past four decades.
It was thought that solar flares were like the snap of a whip — quickly injecting energy before slowly dissipating. Now seeing slow-building flares in such high quantities may change that thinking.
“There is thrilling work to be done here,” stated Valluvan who now works in UC San Diego Professor of Astronomy and Astrophysics Steven Boggs’ group. “We’ve identified two different types of flares, but there may be more. And where do the processes differ? What makes them rise and fall at different rates? This is something we need to understand.”
JOURNAL
Solar Physics
METHOD OF RESEARCH
Data/statistical analysis
ARTICLE TITLE
Solar Flare Catalogue from 3 Years of Chandrayaan-2 XSM Observations
Lopsided galaxies shed light on the speed of dark matter
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DYNAMICAL FRICTION. THE PANELS DEPICT SPARSE AREAS OF THE UNIVERSE WITH DARK COLOUR AND DENSE AREAS WITH LIGHT COLOUR. THE UPPER PANELS SHOW THE DENSITY AROUND A GALAXY IF THE GALAXY'S GRAVITY BENDS (LEFT) OR DOES NOT BEND (RIGHT) THE TRAJECTORIES OF DARK MATTER PARTICLES. THE LOWER PANEL SHOWS THE DIFFERENCE BETWEEN THEM, OR HOW THE GALAXY AFFECTS THE DISTRIBUTION OF DARK MATTER. THE ARROWS REPRESENT THE ACCELERATION CAUSED BY THE OVERDENSITY BEHIND THE GALAXY, FROM WHICH THE FRICTION ON THE CENTRE OF THE GALAXY IS DEDUCTED. SINCE THE ARROWS HAVE DIFFERENT DIRECTIONS AND STRENGTHS IN DIFFERENT AREAS, THE TIDAL FORCES ARE ABLE TO CHANGE THE SHAPE OF A GALAXY.
view moreCREDIT: RAIN KIPPER
So how can the speed of dark matter be measured? The prerequisite is to find a galaxy in the universe that moves relative to dark matter. Since everything in the universe is in motion and there is a great deal of dark matter, it is not difficult to find such galaxies.
Heavy objects, like galaxies, attract all types of matter, whether it is dark matter or visible matter that we encounter on a daily basis. As dark matter moves past a galaxy, the galaxy begins to pull the dark matter particles towards it. However, the change of speed direction of the particles takes time. Before their trajectory curves towards the galaxy, they already manage to pass the galaxy.
Thus, dark matter particles do not enter the galaxy, but instead move behind the galaxy (see video). Behind the galaxy, therefore, the density of matter increases, and this leads to a slowdown of the galaxy – a phenomenon called dynamical friction. The strength of dynamical friction, in turn, depends on how quickly dark matter particles pass the galaxy, that is, how long the galaxy has time to change the trajectory of the dark matter particles. When particles pass slowly, the density of matter increases closer to the galaxy, causing it to slow down more.
The green dot represents a galaxy, and the upper panels show the movement of dark matter particles past the galaxy (if a galaxy exists in the corresponding panel). The lower panels show the shape of all the trajectories, demonstrating that the gravity field of a galaxy affects the particles of matter, creating an overdensity behind the galaxy. Overdensity again slows down the galaxy and distorts its shape.
Let us assume that the galaxy causing the dynamical friction is not tiny, but large. In this case, the overdensity behind it generates friction of different strengths at different points in the galaxy, as seen in Figure 1. The difference in friction makes the shape of the galaxy more lopsided. We experience a similar change in shape on Earth as tidal cycles – high tides and low tides caused by the gravity of the moon.
It is irrelevant how big the dark matter particles eventually turn out to be – their orbit still curves behind the galaxy. The method might not produce accurate results if the particles were comparable in size to the galaxies themselves. However, these dark matter models are already excluded.
Finding the lopsided galaxies themselves is not difficult, because they make up about 30 percent of all galaxies in outer space. Of course, a lot depends on how far to look in the outer parts of a galaxy and what level of lopsidedness deems a galaxy lopsided.
Also, the lopsided shape of a galaxy may not be caused only by dynamical friction. There are a number of other reasons for that. For example, galaxies that were formed after the collision of several galaxies may be asymmetric. In this case, however, we should be able to detect somewhere inside the galaxy the nucleus of another galaxy or a larger stellar halo. Galactic lopsidedness can also be caused by a constant inflow of gas. In such situations, the shape of the galaxy will take a few billion years to recover.
Thus, to measure the velocities of dark matter, we need a lopsided galaxy that is as isolated from other galaxies as possible. In this case, it is more certain that nothing has happened to it other than the passage of dark matter.
In this research, we have figured out how to precisely calculate the forces that affect galaxies in tidal cycles. The next stage is to find galaxies sufficiently lopsided in the universe to study the velocity of dark matter relative to the galaxies.
Cosmology is an important test polygon of theoretical physics. Calculating the speed of dark matter can be important for testing new dark matter models and lifting the veil of secrecy over the nature of dark matter.
Dynamical friction video [VIDEO] |
METHOD OF RESEARCH
Data/statistical analysis
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Back to the present: A general treatment for the tidal field from the wake of dynamical friction
Fledgling planets discovered around a newly formed star
Six-exoplanet system offers glimpse into planet formation and evolution
Peer-Reviewed PublicationIMAGE:
AN AMUSING RENDITION OF THE TOI-1136 SYSTEM IF EACH BODY IN THE SYSTEM WERE A DUCK OR DUCKLING.
view moreCREDIT: RAE HOLCOMB/UCI
With an arsenal of advanced technology, scientists have found a multi-planet star system that provides a rare insight into the way planets form and behave around a very young star.
TOI-1136 is a dwarf star in the Milky Way galaxy more than 270 light years from Earth, which is considered nearby, as the Milky Way is 100,000 light years in diameter. There are six confirmed planets orbiting the star, and scientists strongly suspect the presence of a seventh.
“Because few star systems have as many planets as this one does, it’s getting close in size to our own solar system,” said Tara Fetherolf, visiting assistant professor of astrophysics at Cal State San Marcos and co-author of a new paper about the system. “It’s both similar enough and different enough that we can learn a lot.”
Published today in The Astronomical Journal, the paper offers precise measurements of the exoplanets’ masses, details about the shape of their orbits, and characteristics of their atmospheres. Details like these were built upon initial observations of the system from 2019 using data from the Transiting Exoplanet Survey Satellite, or TESS.
Stephen Kane, UC Riverside planetary astrophysics professor and principal investigator of the TESS Keck Survey, explains how the newly discovered system differs from many other known systems. To begin with, its age sets it apart. At a mere 700 million years old, it’s very young compared to our own solar system, which is 4.5 billion years old.
“This gives us a look at planets right after they’ve formed, and solar system formation is a hot topic. Any time we find a multi-planet system it gives us more information to inform our theories about how systems come to be and how our system got here,” Fetherolf said.
Juvenile stars are both difficult and special to work with because they’re so active. Magnetism, sunspots and solar flares are more prevalent and intense during this stage of a star’s development, and the resulting radiation blasts and sculpts planets, affecting their atmospheres.
“Young stars misbehave all the time. They’re very active, just like toddlers. That can make high-precisions measurements difficult,” Kane said.
All the planets are of a similar age in the system, and formed under similar conditions. “This will help us not only do a one-to-one comparison of how planets change with time, but also how their atmospheres evolved at different distances from the star, which is perhaps the most key thing,” Kane said.
Because all the planets in this system are relatively close together, the research team was also able to measure something that is hard to gauge in other systems.
“Normally when we’re looking for planets, we’re looking at the effect the planets have on their star. We watch the star move around and interpret that as the gravitational effects the planets are having on it. Here, we can also see the planets pulling on each other,” Kane said.
Using the Automated Planet Finder telescope at the Lick Observatory on California’s Mount Hamilton and the High-Resolution Echelle Spectrometer at the W.M. Keck Observatory on Hawaii’s Mauna Kea, the researchers detected slight variations in stellar motion that helped them determine the mass of the planets with unprecedented precision.
To obtain such exact information on the planets, the team built computer models using hundreds of observed velocity measurements layered over transit data. Corey Beard, lead author of the paper and a UC Irvine Ph.D. candidate in physics, said combining these types of readings yielded more knowledge about the system than ever before.
“It took a lot of trial and error, but we were really happy with our results after developing one of the most complicated planetary system models in exoplanet literature to date,” Beard said.
Joining UC Irvine and UC Riverside on this study were researchers from Spain’s Astrophysics Institute of the Canary Islands; the California Institute of Technology; Sweden’s Chalmers University of Technology; Maryland’s Johns Hopkins University; Spain’s University of La Laguna; Sweden’s Lund University; Poland’s Nicolaus Copernicus University; New Jersey’s Princeton University; Japan’s Ritsumeikan University; California’s SETI Institute; Maryland’s Space Telescope Science Institute; the University of California, Santa Cruz; the University of California, Berkeley; the University of California, Los Angeles; the University of Hawaii; the University of Chicago; the University of Kansas; Indiana’s University of Notre Dame; Australia’s University of Southern Queensland; and Connecticut’s Yale University. Funding was provided by the W.M. Keck Foundation, NASA and the National Science Foundation.
Signs of life on Earth appeared almost immediately after the formation of our solar system during the Archean period 3.9 billion years ago. Though TOI-1136 is too close to most of its planets to make life likely – the radiation would be too intense – the team hopes that observing this system ultimately answers existential questions about how our planet came to be.
“Are we rare? I’m increasingly convinced our system is highly unusual in the universe. Finding systems so unlike our own makes it increasingly clear how our solar system fits into the broader context of formation around other stars,” said Kane.
Artist rendering of the TOI-1136 system and its young star flaring.
CREDIT
Rae Holcomb/Paul Robertson/UCI
JOURNAL
The Astronomical Journal
ARTICLE TITLE
The TESS-Keck Survey XVII: Precise Mass Measurements in a Young, High Multiplicity Transiting Planet System using Radial Velocities and Transit Timing Variations
ARTICLE PUBLICATION DATE
29-Jan-2024
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